The present invention relates to an apparatus for producing a multilayered film composite from sealed-together plastic films, having a number of supply rolls, on which the plastic films in web form are wound, as well as to a process for producing a multilayered film composite from biaxially and/or monoaxially stretched and/or unstretched thermoplastic, coextruded plastic films, which are provided on at least one side with a sealing layer, by sealing under pressure and heat application.
In various industries, such as machine design, vehicle and aircraft engineering, or safety technology, there is an increasingly great interest in high-strength film composites and composite bodies both in the form of webs and semi-finished products, such as boards, as well as finished components. Following this development, board producers are working on techniques for the production of products which can be subjected to higher mechanical loads. At the same time as the polymer materials intended for board production are being modified by the incorporation of reinforcing materials, such as textile, glass or carbon fibers, techniques for producing intrinsically reinforced boards by orienting measures are being developed. Examples of these techniques are roll press stretching or the process described in EP-A 0 207 047, the essential measure in that process being compressing a plurality of biaxially stretched films, provided with thin, coextruded sealing layers, into a homogeneous board of any thickness, with application of pressure and heat. For this purpose, in general a stack of films is laid between two pressing plates and introduced into discontinuously operating, hydraulic plate presses of single or multi-daylight design. The pressing operation is determined by process parameters, such as pressure, temperature and time. Time in particular is a problem in the inexpensive production of composite laminates, especially in the case of heating through very thick boards. Continuous run-through presses, in particular twin-belt presses, represent a practicable, time-saving solution in this respect, but can be only used to a limited extent in view of the speeds which can be achieved on them.
German Patent 3,530,309 describes a process and an apparatus for continuously producing thermoplastic webs, in particular for further processing into boards or films, from at least one extruded thermoplastic web heated to processing temperature, which in the heated state is cooled between two fixedly arranged pressure plates, so that the surface of the thermoplastic web is calibrated and smoothed. The cooling of the thermoplastic web is performed under the action of surface pressure, for which purpose it is guided during cooling between two continuously moving, endlessly circulating pressing bands. At the same time, a uniform surface pressure is exerted from the pressure plates hydraulically or mechanically on the inner sides of the moving pressing bands and is transferred from these to the thermoplastic web. The pressure plates are kept at a lower temperature than the final temperature of the thermoplastic web, in order to maintain a temperature gradient between the thermoplastic web, pressing band and pressure plate. The cooling of the thermoplastic web takes place by heat from the web being dissipated via the pressing band to the pressure plates by means of heat conduction. The surface pressure acts throughout the entire duration of the cooling of the thermoplastic web between the pressing bands.